The invention relates to a lightweight building material comprising expanded perlite as an additive and a bonding agent structure consisting of an alkalisilicate, preferably water-glass, e.g. sodium-, potassium-, lithium-water-glass or guanidinesilicate, a partly organic water-glass. The invention also relates to a method for producing the lightweight building material.
A lightweight building material comprising expanded perlite as an additive, and a bonding agent structure consisting of an alkalisilicate, is known from German AS No. 2,745,750. In order to prevent blooming (i.e. salt crystallization at the surface), additives such as zinc, borate, calcium, magensium or a mixture thereof, and calcium nitrate, calcium phosphate, calcium orthophosphate, or a mixture thereof, are added to the mortar mixes for producing the building material. In addition to perlite, the known lightweight building material may also contain expanded clay, foamed glass, vermiculite or foamed diatomaceous earth.
In addition to this, German OS No. 2,813,473 discloses lightweight building materials having uniform porosity and made of a mixture of an aqueous alkalisilicate solution and aluminum and/or silicon powder as the pore forming agent, as well as active, and possible inactive, substances in the presence of an expansion regulator in the form of a methylester and or a propylenecarbonate. Cement, anhydrite or slaked lime may be used as active substances. Inactive substances may be kaolins, clays, bentonites, silicic acids, silicates, gypsum, argils, carbonates and fly ash.
German AS No. 3,001,151 discloses a method for the production of mainly light ceramic items by moulding, drying and firing a raw ceramic mass of clay, clay minerals as lightweight additives, plastic particles and/or hollow bodies, water-glass and a water-glass hardener. In this case, the lightweight additives, the water-glass, the water-glass hardener, and the raw ceramic mass are placed separately in a mould, after which the mass is dried and fired as usual, additional porosity being obtained by burning out the plastic particles. When the ceramic mass is fired, the plastic particles release gases which must be safely disposed of.
German OS No. 2,948,778, moreover, discloses a thermal-insulating material comprising a self-supporting inorganic insulating foam made of an organic basic material which is foamed under the action of heat, the foam structure consisting essentially of water-glass foamed under the action of heat. An insulating material of this kind has very little strength. For this reason, provision is made for the foam structure to be produced on a metal foil to which it adheres during the foaming action.